#include<stdio.h>
#include<math.h>
int main()
{
	int a,b,c,i;
	double sum=0.0,sum1=0.0,sum2=0.0,sum3=0.0;
	scanf("%d %d %d",&a,&b,&c);
    for(i=1;i<=a;i++){
        sum1+=i*1.0;	
	}
	for(i=1;i<=b;i++){
		sum2+=i*i*1.0;
	}
	for(i=1;i<=c;i++){
		sum3+=1.0/i;
	}
	sum=sum1+sum2+sum3;
	printf("%.2f",sum);
  return 0;
}
